Have recieved localised chest pain for over 2 weeks in a hich the pain has increased, making my breathing slowely shallower, what could be causing it?

Hard to say. It would be best to see a healthcare provider to have this evaluated more fully. It could be something simple like a muscle cramp or pain with a joint in your rib cage, but it could also be something more concerning that is causing you localized pain with breathing. In general we think of things that cause inflammation of the lining around the lungs, including infection or blood clot.